California Sen. Dianne Feinstein is calling for a federal investigation into gasoline price spikes that followed a fire at the Chevron Corp. oil refinery in Richmond.

In a letter sent on Tuesday August 28 to the Federal Trade Commission, Feinstein said the Aug. 6 blaze that damaged the state’s third largest refinery did not affect gasoline supplies as some analysts forecast, yet prices still rose dramatically.

Feinstein said the price of gas in the state reached a high of $4.21, more than double the increase seen in average cost of a gallon of gas in the continental U.S.

On Tuesday, the average price for a gallon of regular gasoline in California was $4.12, up from $3.86 on Aug. 7.

The senator said the spikes “appear to be unjustified by supply and demand fundamentals.”